1. Field of the Invention
The present invention relates to a color filter substrate and a display device including such a color filter substrate.
2. Description of the Related Art
Currently, generally-used liquid crystal display devices are composed in such a fashion that a liquid crystal layer is interposed between a pair of substrates in which electrodes are provided. In a liquid crystal display device for color display, pixels are arranged in a matrix configuration in one of the opposed substrates, and a color layer made of color resin materials colored in red (R), green (G), and blue (B) is arranged in each pixel.
In a liquid crystal display device having such a structure, the pair of opposed substrates are bonded to each other with column-shaped or bead-shaped spacers interposed in a display region displaying an image to thus keep a given space between the substrates. This is for suppressing display irregularity in the display region which is caused mainly due to change in width of the space between the substrates in external load application in the pressing step of panel manufacture, during use, and the like.
While in a light shielding region, only a light shielding layer is arranged, so that the space between the paired substrates is not uniformly maintained. This invites display irregularity caused due to severe change in width of the space between the substrates in the peripheral part of the display region near the light shielding region. The display irregularity lowers the display quality remarkably and also lowers the manufacturing yield. These disadvantages are significant especially in LCDs, ultra-slim LCDs, and the like incorporating a driver in the light shielding region for which developments progresses recently. In the LCDs incorporating the driver in the light shielding region, which must be wide, load application to the surfaces of the substrates increases causing non-uniform changes in width of the space between the substrates. In the case of an ultra-slim LCD having substrates with a thickness of, for example, 0.7 mm or smaller, a load applied to the surfaces of the substrates greatly influences the space between the substrates.
In order to tackle the above problems, it has been proposed to provide column-shaped or bead-shape spacers also in the light shielding region, as shown in FIG. 10 to FIG. 12. FIG. 10 shows a transflective type liquid crystal display device 130 including a reflection region and a transmission region in the display region and column-shaped spacers 180. FIG. 11 shows a reflective type or transmissive type liquid crystal display device 131 including column-shaped spacers 185. FIG. 12 shows a reflective type or transmissive type liquid crystal display device 132 including bead-shaped spacers 188. In each of the liquid crystal display devices 130 to 132, a thin film transistor substrate 135 and an opposed color filter substrate 140 including a color layer 160 are bonded to each other by means of a sealant 141 so as to interpose a liquid crystal layer 150. In each of the conventional liquid crystal display devices 130 to 132 shown in FIG. 10 to FIG. 12, the color layer as in the display region is not formed in the light shielding region 190. Therefore, even when spacers similar to those in the display region are provided, the spacers do not reach the opposed substrate. Accordingly, the light shielding region 190 of one of the substrates easily warps by load application in the pressing step of panel manufacture. This means insufficient effects of suppressing display irregularity expected.
The thickness of the substrate in the light shielding region 190 may be set to the same thickness as that in the display region by forming in the light shielding region 190 spacers that are higher by the height of the color layer than the spacers in the display region. This requires, however, formation of the spacers in the light shielding region 190 in an additional step and is, therefore, inappropriate for solving the problems in view of the manufacturing cost and yield.
In view of the foregoing, in order to solve the above problems, for example, Japanese Unexamined Patent Application Publication 2002-277865 discloses a liquid crystal display device including: an array substrate including pixel electrodes and a switching active element driving the pixel electrodes; a color filter substrate including a color film and a counter electrode for the pixel electrodes on a pattern of a light shielding film; and column-shaped spacers of a predetermined height in a predetermined pattern formed on the color filter substrate at a predetermined density, wherein liquid crystal is sealed in the space between the array substrate and the color filter substrate, and the column-shaped spacers formed outside the display region on the color filter substrate are layered on a color film in at least one color and the light shielding film. Japanese Unexamined Patent Application Publication 2002-277865 describes that the column-shaped spacers outside the display region suppress display irregularity in the vicinity of the peripheral part of the panel.
Japanese Unexamined Patent Application Publication 2005-070442 discloses a liquid crystal display device in which a liquid crystal composition is interposed between a pair of substrates, wherein the display part displaying an image includes a color filter layer formed of at least one kind of coloring resin material in each pixel, the light shielding part along the outer periphery of the display part includes a light shielding layer made of a light shielding resin material and light shielding column-shaped spacers keeping the cell gap between the paired substrates, and the light shielding column-shaped spacers are formed by overlaying a first layer made of a coloring resin material with a second layer made of a light shielding resin material. Japanese Unexamined Patent Application Publication 2005-070442 describes that the liquid crystal display device can make the cell gap uniform and can prevent lowering of the display quality and of the manufacturing yield.
The technical schemes for controlling the width of the space between the substrates disclosed in Japanese Unexamined Patent Application Publication 2002-277865 and Japanese Unexamined Patent Application Publication 2005-070442 are shown in FIG. 13 to FIG. 15. FIG. 13 shows a transflective type liquid crystal display device 151 including the reflection region and the transmission region in the display region and column-shaped spacers 180. FIG. 14 shows a reflective type or transmissive type liquid crystal display device 152 including column-shaped spacers 185. FIG. 15 shows a reflective type or transmissive type liquid crystal display device 153 including bead-shaped spacers 188.
Each of the liquid crystal display devices shown in FIG. 13 to FIG. 15 includes, between the spacers and the like and the light shielding layer, the same color layer 160 as that provided in the display region. This allows the spacers to reach the opposed substrate similar to those in the display region to suppress warp caused by load application to the light shielding region 191, as shown in FIG. 13 to FIG. 15.
In each of the liquid crystal display devices 151 to 153 shown in FIG. 13 to FIG. 15, however, the presence of the light shielding layer spacers below the color layer 160 in the light shielding region 191 increases the width of the space between the substrates in the light shielding layer when compared with that in the display region. This invites swelling of only the light shielding region 191 upon load application to the surfaces of the substrates. Swelling of the light shielding region 191 invites display irregularity caused due to severe change in the width of the space between the substrates in the peripheral part of the display region near the light shielding region 191.